1. Field of the Invention
The present invention relates to vacuum type brake booster devices for vehicular use, designed to operate with the aid of vacuum force principally for actuation of a brake master cylinder in an automotive hydraulic brake system, and more particularly to those of the structure including a booster shell having a brake master cylinder fitted to one end face thereof, an input rod extending through the other end face of the booster shell, and a booster piston accommodated in the booster shell and arranged to actuate the brake master cylinder under the action of the input rod.
2. Description of the Prior Art
With conventional forms of such brake booster device, the booster shell and the booster piston are circular in transverse cross section and, in order to increase the diameter of the booster piston thereby to enhance the capacity of the booster device, the booster shell must necessarily be increased in diameter or radially enlarged, giving rise to the problem of its interference with adjacent vehicle components, such as a clutch master cylinder and an instrument panel, which involves much difficulty in installing the booster.